In many technical applications, engine components or other members are radially nested one within the other, wherein one of the members supports the other. For the support, support assemblies are provided which couple conjugated support points of the members with each other. Upon being charged with a hot fluid flow of rapidly changing temperature, those members may respond to the temperature change with different response times. That means, upon a temperature change of a hot fluid flow, an inner member may follow the temperature change slower or faster than the outer member. This in turn may result in significantly different thermal expansion of the members. It is thus known in the art to provide a support arrangement which allows relative displacement of conjugated support points of the inner and the outer member in a radial direction, that is, a radially floating support assembly is provided. In providing radially floating support assemblies, a relative displacement of conjugated support points is enabled, which in turn enables unobstructed differential radial thermal expansion of the members. In order to ease the assembly and disassembly of the engine, the supports are commonly arranged in one cross sectional plane, or at one axial position. However, if any of the members exhibits a certain magnitude of axial extent, that is, axial ends of the members cantilever from the support points, an axial end of one of the members displaces relative to the other member upon differential thermal expansion of the members. In other words, an axial end of one member will be provided at different axial positions with reference to the other member, dependent on the state of differential thermal expansion. This may lead to detrimental effects if, for instance, an axial end of the inner member is intended to be provided adjacent a further member for the purpose of sealing a flow. This holds in particular true if the axially adjacent members are not fixedly attached to one another, or are intended to perform a relative movement, such as, for instance, if one of the members is a stationary member and the other one is a rotating member in an engine. Differential thermal expansion between the inner member and the outer member may then lead to either large gaps between the axially adjacent members and related leakage flows, or high mechanical pressure between the abutting members, contact between relatively moving engine components, and potentially mechanical damages.
An exemplary instance is found at the first or inlet guide vanes of an expansion turbine of a turboengine, and in particular of a gas turbine engine, and at the interface of a first guide vane row to an adjacent first row of running blades. The inlet guide vanes of an expansion turbine, provided immediately downstream a combustor in case of a gas turbine engine, or, more generally, of a working fluid inlet, are typically supported at an outer radius of the guide vane members and at a hub side of the guide vane members, such as to appropriately support the forces due to the pressure differential over the first guide vane row at the high temperatures present at the first guide vane row. The radially outer end of a first row guide vane member is typically supported by a turbine housing. For aerodynamic reasons, the hub side support may not be provided straight and radially from the housing, but may be provided by the rotor cover which in turn extends an axial distance along the rotor from its own support. It is a well-known fact that, upon a change of the temperature of a working fluid of a turboengine entering the expansion turbine, the rotor cover and the turbine housing respond to the temperature change of the fluid with different time constants. Commonly, the rotor cover follows the working fluid temperature change significantly faster than the turbine housing. This is not an issue if the turboengine operates with a by and large constant temperature of the fluid entering the expansion turbine. In these cases the rotor cover and the housing will be at essentially constant and largely equal temperatures. Thus, both members will experience an essentially equal thermal expansion. Steady state thermal expansion of the housing and the rotor cover may thus be easily accounted for. However, in case of significant load changes of the turboengine, which go hand in hand with changes of the temperature of the fluid entering the expansion turbine, differential thermal expansion of the housing and the rotor cover need to be considered. This becomes most accentuated upon a fast loading of the engine form idle or even standstill to a high engine load. Due to a differential thermal expansion of the rotor cover and the housing of the turboengine, the hub side of the turbine inlet vane is axially displaced with respect to the radially outer side. The vane members tilt, and hub side axial gaps open or close, and may need to be dimensioned larger than required for steady state operation, potentially causing enhanced fluid leakages and related performance degradation at steady state operation. Widening of gaps during operation states without thermal matching of the housing and the rotor cover may cause additional performance penalties during these phases of operation. It may take several hours until thermal steady state and thermal matching is achieved. In today's grid operation, turboengine power plants, and in particular gas turbine and combined cycle power plants, are increasingly used as peak load engines, with frequent significant and fast load changes. The operation times in which no thermal equilibrium of the engine components is achieved, and accordingly significant dimensional mismatch due to differential thermal expansion is present, may thus cumulate to a significant share of the overall operation time, and cumulative performance losses become increasingly relevant for the power plant operator.